Pyrazine and Pyrazine-Pyrimidine Dimers

摘要

Spectra of the pyrazine-d sub 4, pyrazine-h sub 4-pyrazine-d sub 4-pyrimidine dimer are obtained and analyzed with the help of Lennard-Jones-hydrogen-bonding (LJ-HB) potential energy calculations. The pyrazine isotopic hetero- and homo-dimers possess nearly identical spectra with the exception that the perpendicular dimer features are displaced to the red by approx. 11 cm. Exchange or exciton interactions in this system are vanishingly small (less than 1/cm). The geometrics suggested by the isotopically substituted pyrazine dimer spectra are the same as those found for the pyrazine-h sub 4 homo-dimer: a parallel planar hydrogen bonded and a perpendicular dimer. The pyrazine-h sub 4 and pyrazine-h sub 4-pyrimidine dimer spectra are quite complicated. These spectra can be assigned as rising from one parallel stacked head-to-tail displaced dimer, one parallel planar dimer, and 3 perpendicular dimers based on comparisons with spectra of the pyrazine and pyrimidine dimers.